This invention relates to a threading device on a sewing machine for stretching thread in front or at the rear of an eye in a needle and threading the eye with taut thread.
Such threading device is disclosed in Japan Published Unexamined Patent Application No. S63-89194. The threading device includes a stretching member for stretching out thread, a moving member for moving the thread stretched by the stretching member to the front or the rear of an eye in a needle, an operating member for manually operating the moving member, and a threading member such as a threading hook or a threading rod for threading the needle.
However, in the related-art reference, the force, speed and the like of manual operation of the operating member change the position or tension of the thread in front or at the rear of the eye. When the thread cannot reach the operating range of the threading hook or the threading rod, threading operation fails. When the operation amount of the operating member comes short, the momentum of the thread moved by the moving member is insufficient. As a result, the thread cannot reach a given position in front or at the rear of the eye, and the threading hook cannot catch thread.